Production of celeste in a computor organ

ABSTRACT

Apparatus is disclosed for producing a celeste effect in a computor organ of the type wherein musical notes are generated by computing the amplitudes at successive sample points of a musical waveshape and converting the amplitudes to notes as the computations are carried out in real time. Each amplitude is computed during a regular time interval tx by individually calculating and combining at least two sets of discrete Fourier components. The first set includes harmonically related components, generally the true pitch fundamental and overtones of each selected note. Components of the second set are offset slightly higher in frequency from those in the first set. The resultant synthesized sound resembles an organ celeste stop wherein two organ pipes, one tuned slightly sharp with respect to the other, are sounded when a note is played. In one illustrative embodiment, each set contains the same number of components, each component in the second set being slightly higher in frequency than the corresponding component of the first set. In another embodiment, the first set includes plural harmonic components, the second set contains only one component slightly offset from the fundamental of the first set.

[451 May 7,1974

[ 1 PRODUCTION OF CELESTE IN A COMPUTOR ORGAN [75] Inventor: Ralph Deutsch, Sherman Oaks,

' Calif.

[73] Assignee: Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu, Japan 22 Filed: Jan. 5, 1973 21 Appl. No.: 321,231

521 Us. Cl. 84/124, 84/DIG. 4

[51] Int. Cl. GlOh 1/02, GlOh 5/02 [58] Field of Search 84/101, 1.03, l.22l.24, 84/D1G. 4, DIG. 5

[56] References Cited UNITED STATES PATENTS 3,515,792 6/1970 Dcutsch....,. 84/1.03

3,610,799 /1971 Watson 84/l.01 3,696,201 10/1972 Arsem et al. 84/1.01

3,697,661 10/1972 Deutsch i 84/101 3,740,450 6/1973 Deutschm. 84/].24 3,743,755 7/1973 Watson.....' 84/l.0l

3,755,608 8/1973 Dcutsch 84/l.01 3,763,364 10/1973 Dcutsch et a1... 84/103 X 3,681,531 8/1972 Primary Examiner-Richard B. Wilkinson Assistant ExaminerStanley .l. Witkowski Attorney, Agent, or Firm Howard A. Silber; Flam& Flam Burkhard et al 84/124 X 571' ABSTRACT Apparatus is disclosed for producing a celeste effect in a computor organ of the type wherein musical notes are generated by computing the amplitudes at successive sample points of a musical waveshape and converting the amplitudes to notes as the computations are carried out in real time. Each amplitude is computed during a regular time interval 1, by individually calculating and combining at least two sets of discrete.

Fourier components. The first set includes harmonically related components, generally the true pitch fundamental and overtones of each selected note. Components of the second set are offset slightly higher in frequency from those in the first set. The resultant synthesized sound resembles an organ Celeste stop wherein two organ pipes, one tuned slightly sharp with respect to the other, are soundedwhen a note is played.

ln one illustrative embodiment, each set contains the same number of components, each component in the second set being slightly higher in frequency than the corresponding component of the first set. In another embodiment, the first set includes plural harmonic components, the second set contains only one component slightly offset from the fundamental of the first set.

16 Claims, 6 Drawing Figures smi ng, (12+J) for n-l. 7 I3 E n l2 tor n= l.2---8 HARMONIC slNUSOlD TABLE V AMPLITUDE MULTlPLlER Cl R A F (n) a (n) x, MEMORY ADDRESS n (q n A 2 Fe DEQODER HARMONlC COEFFICIENT 551.4 n nsr nQ,(R+,) MEMORY Id HARMoNlC. m-rznvm. CLEAR 4/ l6 ADDER f 23 L /42 msn'm. To 34 qw pB ANALOG LN MEMO," cowvewrza 7 -45 ADDRESS E CONTROL //5 E 56 4 44 I J EEAY 27 scum: west-EM -32 I! 1 15 meow-mm NOTE INTERVRL ADDER (q GATE $211533 2Q I 1 NOTE mran AL ADDER I 0 "'(C 48 i '18 INSTRUMENT KEYBOARD owlrcnEb p BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to production of celeste in a computor organ.

2. Related Applications The present invention is related to the inventors'copending US. Pat. applications No. 225,883, filed on Feb. 14, 1972, entitled COMPUTOR ORGAN and No. 298,365, filed on Oct. 17, 1972, entitled COMPUTOR ORGAN USING PARALLEL PROCESSING. Those disclosures are incorporated herein by reference.

3. Description of the Prior Art.

The celeste tones of a pipe organ are produced by a multi-rank set of pipes. One rank is set to true pitch, producing tones at the nominally correct 8-foot frequencies. The second rank consists of like sounding pipes, but tuned sharp with respect to true pitch. The frequency offset of the second rank is not consistent over the manual, but typically ranges from about 2 Hz at C (the note ofC in the third octave) to about 4 Hz at C When a note is played, the listener perceives a pleasant beat noteas the sounds from the two ranks interact. This gives the tone a considerable warmth,

In conventional electronic organs a celeste effect is obtained using a separate set of oscillators tuned sharp with respect to the usual analog tone generators. When mixed electrically or acoustically, the combined generator output produce a reasonable semblance of celeste. In another approach, a pseudo-celeste effect is achieved acoustically by using a slowly rotating speaker to reproduce the organ tones.

Celeste cannot easily be produced in a digital organ of the type wherein a stored musical waveshape is repeatedly read from memory at a rate determined by the fundamental frequency of the note being generated. (An instrument of this type is shown in the inventors US. Pat. No. 3,515,792 entitled DIGITAL ORGAN.)

A fundamental characteristic of celeste is an interference or beat effect which occurs between sounds of slightly different frequencies. To synthesize this effect requires production of a waveshape which changes in time. To achieve suchsynthesis in a system which repeatedly reproduces the same stored wave form requires two separate digital organs, one generating a note of true pitch, the other producing a note of slightly higher pitch. The two notes are combined, either electrically or acoustically, to produce celeste. Obviously, such implementation may double the system cost.

The principal object of the present invention is to produce a celeste effect in a computor organ of the type wherein musical notes are generated by individually calculating and combining the Fourier components comprising that note. Toaccomplish this, at least two sets of Fourier components, offset slightly in frequency from each other, are calculated and'combined to synthesize each celeste tone. In effect, this corresponds to generating two notes, one at the true pitch and another tuned sharp. The resultant waveshape is not uniformly repititious, but changes in time; it may be thought of as the superposition of separate waveshapes associated with two notes of slightly different frequency. When this resultant waveshape is reproduced acoustically, a remarkably realistic celeste effect results.

SUMMARY OF THE INVENTION As described in the above mentioned patent application entitled COMPUTOR ORGAN, musical notes are produced by computing in real time the amplitudes at 'successivesample points of a musical waveshape, and converting these amplitudes to notes as the computations are carried out. In accordance with the present invention, the amplitude at each sample point is obtained by summing at least two sets of Fourier components, one associated with the true pitch of the selected note, the other set being offset, generally slightly higher in frequency therefrom. The two sets of Fourier components thus may be considered as synthesizing respectively the true pitch and tuned-sharp ranks of a pipe organ celeste stop.

In one typical implementation, described in conjunction with FIGS. 1 and 2 below, the first set of Fourier components includes the fundamental and second through'eighth harmonics of the selected note. These true pitch components are illustrated by the solid lines in the spectrum of FIG. 2. The second set of Fourier components includes a fundamental having a frequency slightly higher than that of the first set, and seven overtones harmonically related to this shifted fundamental, and hence all offset in frequency with respect to the first set. The offset or frequency-shifted components are indicated by broken lines in the spectra of FIG. 2. v

The. circuitry of FIG. 1 calculates both the true-pitch and frequency-offset Fourier components during each computation time interval The components are summed to obtain the waveshape amplitude at the sample point currently being evaluated. The computations are repeated during successive time intervals I to generate a waveshape which when acoustically reproduced yields a realistic celeste sound. The use of two component sets each having eight harmonics is quite satisfactory to synthesize a flute or soft string voice.

In the alternative embodiment of FIG. 3, a greater number of true pitch harmonics are generated, as indicated by the solid lines in the spectrum of FIG. 4. A rich string voice can be synthesized. The celeste effect is produced by. a singleharmonic component (shown as a broken line in FIG. 4) having a frequency slightly higher than the true-pitch fundamental. The resultant offset celeste rank has a sinusoidal" waveform tuned sharp with respect to the first rank.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a harmonic spectrum associated with the computor organ of FIG. 1.

FIG. 3 is an electrical block diagram of a computor organ configured for production of celeste and wherein only a single frequency-shifted component is generated.

FIG. 4 is a harmonicspectrum associated with the computor organ of FIG. 3.

selected notes.

- 3 FIG. 5 is a simplified electrical block diagram of circuitry useful in conjunction with thecomputor organ of FIG. 3 for inhibiting production of celeste for certain FIG. 6 is an electrical block diagram showing celeste generation in a parallel processing computer organ.

DESCRIPTION or THE PREFERRED I EMBODIMENTS The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely-for the purpose of illustrating the general principles of the invention since the scope of the invention best is defined by the appended claims.

teristics are obviously inapplicable or unless specific" exception is made.

The computor organ 10 of FIG. 1 produces via a sound system 11 musical notes having a celeste quality.

For each note selected'by the keyboard switches '12, the computor organ 10 computes the amplitudes at successive sample points of a waveshape characterizing the selected note. Each amplitude is obtained by calculating two sets of discrete Fourier components as illustrated in FIG. 2.

Both sets of components are-summed algebraically in an accumulator 13 which, at the end of each computa tion time interval 1, contains the amplitude for the current sample point. This amplitude is provided via a gate 14, enabled by the t,'signal on a line 15, to a digital-toanalog converter 16 which supplies to the sound system l1 a voltage corresponding to the waveshape amplitude just computed. Computation of the amplitude for the next sample point subsequently is initiated, so that the analog voltage supplied from the converter 16 comprises a musical'waveshape generated in real time. The

resultant sound, synthesized from true pitch and frequency-ofi'set harmonic components. realistically simulates a multi-rank Celeste tone.

The period of the computed waveshape. and hence the fundamental frequency of the generated note. is'es= tablished by a frequency number R selected by the keyboard switches 12. A set of such frequency numbers corresponding to the notes of the instrument is stored in afrequency-number memory 17. Each true pitch Fourier component Ff'" is calculated in accordance with the following equation:

on sin (Qqr/N) nqR for q l. 2. 3

where R is the frequency number mentioned above, and n I, 2, 3, A designates the Fourier component during evaluated. The'value n 1 corresponds to the fundamental, n 2 to the second harmonic, n 3 to the third harmonic andso forth. The harmonic coefficient C, specifies the relative amplitude of n'". Fourier component. The value of R- designates each sample point of the waveshape being generated.

Similarly, each frequency-offset Fourier component F,,"" is calculated in accordance with the following equation:

4 1 =.C,, sin (21r/N) no (R 8) for 'q l 2, 3

where again n l, 2, 3, B designates which order Fourier component is being evaluated. The harmonic coefficient C,,' specifies the relative amplitude of the n" Fourier component in the shifted-frequency set. The value 5 determines the extent. of frequency-offset with respect to the corresponding true-pitch component. This value 8 may be the same forall notes, or may be different for each note or groups of notes. Appropriate values of 8 are stored in 'a memory 18 (FIG. 1) accessed in unison with the frequency number memory 17 as each keyboard switch 12 is selected.

The value N designates the number of amplitude sample points computed forthe note of lowest pitch .(fundamental frequency) of the computor organ l0.

Satisfactory synthesis of pipe organ sounds is achievedusing 32 such sample points (N 32). Preferably the total number (A B) of components calculated to synthesize the waveshape is equal to or less than N/2. This will satisfy the well known sampling rate requirements (related to the Nyquist criteria) of a sampled data system. In the embodiment of FIG. 1, the computor organ 1Q calculates eight Fourier components (A 8, B 8) for each of the two sets combined to obtain each waveshape sample point amplitude. Accordingly, the sample point amplitude X (qR) is given by the relationship:

. ,4 8 A g I 2 X00112): 2 FAQ) 2 F30): Cu SlH N "QR v .8 211" 2 si n m rs which all form of discrete Fourier representation of a equation 1) above. The eight frequencyehifted components (broken lines in FIG. 2) are calculated during the subsequent calculation intervals term through ta in accordance with'equation (2) above. All-of the calculated components are summed in the accumulator 13, thecontents of which, representing the amplitude .value it. (qR), is gated to the digital-to-analog converter 16 at the end of the computation cycle t To this end, the clock 20 provides timing pulses at intervals t via a line 22 to the counter 21. The counter 21 preferably is of modulo 16, and provides outputs t through [CF16 on the lines designated with corresponding numbers. The signals r through r all are provided via an OR-gate23 onto. a line 24 to control calculation of the true-pitch components. Similarly, the signals r through t all are supplied via an OR-gate 25 to a line 26 which controls calculation ofthe frequency-offset components. The 1 signal, slightly delayed the eight true-pitch components note is supplied from the memory 17 via a line 28395;! 5 interval adder 34. Accordingly, the contents of the a gate 29 to a note interval adder 30. The gate 29 is enadder 34 represents a quanitity nq(R 8) for n l, 2, abled by the I, r signal, 50 that the contents Of the adder 3, 8 where now indicates the harmonic order of 30 is incremented each computation interval, and repthe frequency-shifted Fourier components illustrated resents the value (qR) designating the waveshape samby the broken lines in FIG. 2. ple point currently being evaluated. 10 The memory address decoder 35 now accesses from At eachinterval r t through r the value (qR) is the sinusoid table 36 the value sin (21r/N) nq(R 8) gated from the adder 30 via a line 32 and a gate 33 to corresponding to the argument nq(R 8) received a harmonic interval adder 34 which is cleared byvthe t, from the harmonic interval adder 34 on the line 37. signal at the beginning of each computation cycle. Ac- This sin value, supplied via the line 37, is multiplied by cordingly, during the first eight calculation cycles, the the appropriate harmonic Coefficient n' Obtained from contents of the adder 34 represents the value nqR (for the harmonic coefficient memory 41. The memory adn l, 2, 3, 8) designating which true-pitch hardress control 42 now receives the signals through monic component currently is being evaluated. t on the line 26, insuring that the appropriate values An address decoder 35 accesses from a sinusoid table ciggejlgpplied tg the multiplier V W V 7 36 the value in (Zn/N) nqR corresponding to {he arg The output of the multiplier 38 Oh the line 39 reprement nqR received via a line 35 from the harmonic in- SeIltS the Value e of the frequency-Offset component terval adder 34. The sinusoid table 36 may comprise a currently being ealethated- This Value is pp to t d l memory Storing values f i (Z /N) '0 f accumulator 13'where it is summed with the previously 5 0 N at intervals of D, where D is called the reso- Calculated true-Pitch and frequency-Shifted compo lution constant f the memory nents. When all eight frequency-shifted components The value Sin gi nqR supplied via a he 37 is have been evaluated (i.e., after interval t the conmultiplied by the coefficient C, for the corresponding tents of the accumulator 13 represents e Value 0 n'" harmonic by a multiplier 38. The multiplication (q as given y qp above. The 1 slgnal gates product represents h amplitude f the this value x (qR) vla the dlgltal-to-analog converter 16 true-pitch harmonic component, and is supplied via a t the SPuhd System h Clears the aeeumhlatot line 39 to the accumulator 13. The appropriate coeffi- 1h rehdlhess for comphtahohhof the shmple polht cient C is accessed from a harmonic coefficient mem- I P As the comphtahohs are earned the ory 41, described in more detail below, under direction Sound phodhcedhy the System 11 corresponds to of a memory address control unit 42 also receiving the Selected notes wlth a Pleashg Celeste tcomputation interval signals 2, through r from the The memory 41 hh h h' a read line only memory conta ning harmonic coefficient values After the eighth true-pitch component has been caland appmpnate to produce a note of deslrhd culated, the harmonic interval adder 34 is cleared. To tonal quahty' The Values may the same, or accomplish this the the [m8 Signal slightly delayed by ferent from the valu s C, for like harmonics. In the a delay unit 44, is supplied via a line 45. to the clear F frequemy'fhset monic component (broken lines in FIG. 2) will have an Input of h adder r amplitude equal to the corresponding true-pitch com-' To compute the frequency-Offset Components, the ponent. This in effect will synthesize a pipe organ Value 5 associated with the Selected note is accessed sound wherein both celeste ranks are of like tonal qualfrom the memory 18 and added to the frequency 45 ity. Alternatively, the values C may differ from the ber R fOI' that note an adder Circuit 46. The Sum corresponding value C producing a sound wherein i iS supplied t0 3. second note interval adder 47 via the two celeste ranks have different voices a gate 48 actuated by the computation n rv l ign The following Table I indicates typical values of C,, II On the line 15. Accordingly, the note interval adder and C for a flute voice and a soft string voice respec- 47 during each computation interval will contain the tively wherein both celeste ranks are of like voice (C. sum q(R 6). This value q(R 8) in effect represents C,,) and for a celeste stop having ranks of different the sample point of a waveshape having a fundamental tonal quality (C 9* C,,'). I

TABLE I slightly higher in frequency, by an amount designated by 8, than the t lfue-pitch fundamental of the same note.

At each interval i through 1 the value q(R '0) is supplied viaa line 49 and a gate 50 to the harmonic Value Stored in Memory Flute Soft String Mixed Voice Harmonic (Relative Decibel Equivalent (Relative db Equivalent (Relative db Equivalent Coefficient Amplitude) Amplitude) Amplitude) C, 127 0 127 0 127 0 C 0 50 40 IO 40 lO C 4 30 l6 l8 l6 1 8 C 0 SO 36 -*l l 36 l 1 C 0 50 6 27 6 27 c, 0 50 4 30 4 -30 C 0 50 5 29 5 29 c 0 50 l 44 1 +44 C, 127 0 C Same Same 0 50 C as as 4 30 C C,-C,, C,C 0 50 C respectively respectively 0 50 TABLE 1- Continued Value Stored in Memory Flute Soft String Mixed Voice Harmonic (Relative Decibel Equivalent (Relative db Equivalent llelative db Equivalent Coefficient Amplitude) Amplitude) Amplitude) 'c.,' m so W The harmonic coefficient memory 4 l and add};

mrgafi calculates l5 true-pitch Fourier compo- ,nents Ff" (forn= l, 2, 3, ,15) and asingle compothe binary output of which may be supplied directly to l the address control input of the type 8223 memory. A Signetics type 8250 binary-to-octal decoder may be used in conjunction with the type 8281 counter to provide the separate t through [m signal linesshown in FIG. 1. The type 8223 memory may be programmed to store the harmonic coefficients listed in Table 1 above, or other values of C and C appropriate to produce other celeste voices.

' The frequency number memory 17 and the 8 memory 18 likewise may be implemented using the same or separate conventional integrated circuit read only memories such as the Signetics type 8223. The I following table shows typical values for the frequency number R and 8 values for the notes between C and C TABLE 11 Note R 8 Frequency Offset of hifted FundamentaKHcrtz) D, 0.0382 0.006 2.20 D#;. 0.0405. 0.006 2.25 1 E 0.0429 0.006 2.35

G 0.0510 0.007 2.60 (i#;i 0.0541 0.007 2.70

C and assume a monophonic instrument as shown in FIG. 1. The listed 8 values will provide the frequencyoffset between the true-pitch and frequency-shifted I fundamental components also specified in Table II. The

nent F offset slightly higher in frequency than the true-pitch fundamental. The associated harmonic spectrum is shown in FIG. 4. The true-pitch components are calculated during the time intervals t through 1 24 and the offset component is evaluated at the calculation interval r To this end, the corresponding r through t outputs from the counter 21 are supplied via an OR- gate 52 and a line 53 to the'gate 33. Thus the value nqR in the harmonic interval adder 34 is incremented at each of these 15 consecutive calculation intervals. Ac-

cordingly, the true-pitch componentvalues F,,"" for n 1,2, .,l5 successively are provided on the line 39' for summation in the accumulator 13. After the-15th true-pitch component F has been calculated, the harmonic interval adder 34 is cleared by the 5,, signal, slightly delayed by a delay unit 54.

The single frequency-offset component is calculated during the interval t At the beginning of each computation cycle, thevalue 8 associated with the selected note is accessed'from the memory 18 and supplied via a gate 55 to an interval adder 56. The value 8 is added to the previous contents of the interval adder 56, so that the output 'on a line 57 represents the value q8. This is summed with the value qR from the note interval'adder 30 by an adder 58 to obtain the value q(R 8). Atthe calculation interval t the value q(R 8) is supplied from the adder 58 via a gate 59 to the harmonic interval adder 34' upon occurrence of the r signal on a line 60. Sincethe adder 34 previously was cleared by the delayed signal, theresultant contents of theadder 34 will be simply q'(R 8). i

The memory address decoder 35 then'accesses from the sinusoid table 36 the value sin (2/N) q(R 8) cor- 8 values are a design choice selected to provide a pleas ing celeste. In the example of Table 11, different groups of notes have like frequency offset. As mentioned before, this is not necessary, and all notes could have the same offset, or each note could have a different frequency offset.

In the alternative embodiment of FIG. 3, the compuresponding to the argument q(R 8) received from the adder 34-. That sin value, provided via the line 37, is

multiplied by the corresponding coefficient C," to providethe value F c,' sin (211f/N) q'(R a This value F is added in the accumulator 13 to the sum of the previously calculated l5 true-pitch components, to provide the samplepoint amplitude This value of X (qR) then is gated-via the digital-toanalog converter 16 to the sound system 11.Again there results a note having pleasant celeste characteristics. v

leste sound. produced by the computor organ '10 of FIG. 3. The 15 true-pitch components are indicated by the solid lines, and the single frequency-offset component by the brokenline. The relative amplitudes of the various components of course determine the tonal FIG. 4 shows a typical harmonic spectrum of the cequality of the produced sound. By way of example, a

rich string sound may beproduced using the harmonic component values C and C listed in the following Table III. These values are stored in the harmonic coefficient memory 41 and appropriately accessed by the memory control 42 which receives the calculation interval signals on the lines 53 and 60.

TABLE III Harmonic Value Stored in Memory Coefficient Rich String Voice (Relative (Decibel Amplitude) Equivalent) Celeste may be implemented for all notes of the organ, or only for some notes. Thus in the embodiment of FIG. 3, celeste is produced for each note between C;, and C Celeste may be inhibited, as by appropriate logic 62, when a note between C and B or between D, and C-, is selected.

Illustrative celeste inhibit circuitry 62 is shown in FIG. 5. The lines C and B and B through C from the corresponding keyboard (or pedal) switches 12 are supplied on an OR-gate 63. When a note between C;, and C is played, a low output is present on the line 64 from the OR-gate 63, indicating that celeste is to be implemented. This low signal is inverted by an inverter 65 to'produce on a line 66 a high signal which enables a pair of AND-gates 67, 68. The gates 67, 68 thus provide the I,.,,, and u signals respectively to the delay unit 54 and the gate 59, as shown in FIG. 3. Normal celeste production occurs.

When a note between C and B or between B and C is played, the output of the OR-gate 63 on the line 64 is high. This functions as described below to inhibit celeste production. During the calculation interval t the offset harmonic component F,, is not generated. Instead, a 16th (n 16) true-pitch harmonic F is produced.

When the output of the OR-gate 63 is high, the output of the inverter 65 is low, and the AND-gates 67, 68 are disabled. The t is not supplied to the delay unit 54, hence the harmonic interval adder 34' is not cleared at the end of the r interval. Further, the high signal on the line 64 enables an AND-gate 69, which provides the pulse via an OR-gate 70 to the gate 33. As a result, during the time interval 1 the value (qR) is added to the contents of the harmonic interval adder 34', so that the contents becomes nqR l6qR. As a result, the sin value corresponding to that argument l6qR) is accessed from the sinusoid table 36 and to-the harmonic amplitude multiplier 38.

Similarly, the 1 signal is provided via the AND- gate 69 to the memory access control 42'. This causes access from the harmonic coefficient memory 41 of the value C16 (that is, the harmonic coefficient for the 16th true-pitch harmonic). As a result, the true-pitch harmonic F is provided to the accumulator 13. The resultant waveshape is obtained from 16 true-pitch harmonics and no frequency-offset components; this corresponds exactly to the production of a true-pitch note without celeste.

As shown in FIG. 6, production of a celeste readily is implemented in a computor organ using parallel processing. The organ 75, like the instrument of FIG. 1, calculates the same number of true-pitch and frequency-shifted components. The advantage of using parallel processing is that both sets of Fourier components are calculated concurrently, so that the system clock rate may be one-half that required for the computor organ 10 of FIG. l. As discussed in the above mentioned patent application entitled COMPUTOR ORGAN USING PARALLEL PROCESSING, this significant reduction in computation rate more readily permits the computor organ to be implemented using conventional integrated circuitry. Referring to FIG. 6, the computor organ 75 includes a first processing channel 76a in which the values 1 for the true-pitch components are calculated, and a second, like parallel processing channel 76b wherein the values F are calculated for the frequency-shifted components. System timing is established by a clock 77 having a rate one-half that of the clock 20 in FIG. 1. The output pulses t from the clock 77 advance a binary counter 78 of modulo 8. The output of the counter 78 on the lines 79a, 79b, 790 comprises a binary signal representing the respective counts t through t At the first interval r the low order, true-pitch Fourier component F is calculated in the channel 76a and concurrently the low order frequency-shifted component F is calculated in the channel 76b. These components, present on the respective lines 80, 81 are .summed by an adder 82 and supplied via a line 83 to an accumulator l3, gate 14, digital-to-analog converter 16 and sound system 11 like that of FIG. 1. At consecutive intervals 1 5 through 1, successive pairs of truepitch and frequency-shifted components F,," and F,," for values n 2,3, 8 are computed, summed in the adder 82 and supplied to the accumulator 13. In this manner, both sets of Fourier components are computed during eight time intervals 1 each of which intervals t is twice as long as the calculation interval I of the FIG. 1 system.

The various components of the parallel processing organ 75 will be recognized by reference to FIG. 1. However, separate harmonic interval adders 34a, 34b are used to accumulate the totals nqR and nq(R 8) respectively. Both adders 34a, 34b are cleared by the 2,, signal derived via a delay unit 84 from the t signal. The values qR from the note interval adder 30a and q(R 8) from the note interval adder 30b respectively are gated to the harmonic interval adders 34a and 34b via gates 33a and 33b enabled at each calculation interval 1 through r The timing signals t through r are derived from the binary counter 78 output using a binary-tooctal decoder 85. The eight lines from the decoder 85, containing the respective signals 1, through I,.,,,,' all are connected to an OR-gate 86 the output of which, on a line 87, enables the gates 33a and 33b.

Separate harmonic coefficient memories 41a, 41b and associated address control units 42a, 42b are used in the respective channels 76a, 76b. Each may be implemented using a Signetics type 8223 read only memory or the equivalent, the address control portion of which directly receives the binary coded count on the lines 790 79c. The memory 41a contains the truepitch harmonic coefficients C and the memory 41b 5 stores the coefficients C,, for. the frequency-shifted components. These values may correspond to those set forth above in Table I.

Although the embodiments shown in the drawing s vention is not so limited. Thus three or more sets of components could be evaluated and summed to obtain each sample point amplitude. In such case, all three sets may be slightly offset in frequency from each other. Further, even in the two set embodiments, it is not required that the components of either set correspond in frequency to the true pitch of the selected note. Thus, e .g., one set may be tuned slightly below true pitch, the other slightly above. Advantageously,

adders 30,47

' Harmonic interval adder 34 R+8 Adder 46 Gates 14,29,14 48,50

Sinusoid table 36 and memory address decoder 35 Harmonic coefficient memory 41 and memory address control 42 Harmonic Amplitude Multiplier 38 Accumulator l3 logic element [p. 37]

(b)SlG. 8268 gated full adder [p. 97]

(c)Tl SN5483, SN7483 4-bit binary full adders [p. 9-271] (may be connected as shown in Flores Section ll.l to accumulate sum) Same as note interval adder 30 SIG. 8268 gated full adder Tl SNS408, SN5409 quadruple AND gates [p. 6-17] (b)Tl TMS4400 ROM containing 512 words of eight-bits [p. l4-l88] programmed to store sin values (a)SlG 8223 read only memory which in- See Table l for eludes address examplary control circuitry I contents (b)TI.SN54 l 66 series shift registers [p.9- 1 34 (a)Ma'y be implemented as shown in application sheet, SIG. catalog, p.28 using SIG 8'202 buffer registers and 8260 arithmetic element 7 (b)Also can be implemented usingv SlG 8243 sealer [p.65]

(a)SlG 8268 or Tl SN5483.

SN7483 full adders connected as shown in Flores. section l LI g Y 10 but not necessarily; the musical instruments disclosed each calculate two sets of Fourier components, the inherein are implemented digitally.

Conventional'lnte- Component grated Circuit (or V (FIG. 1) other reference) g V Remarks Frequency (a)SlG 8223 field-pronumber grammable read only memory 17 memory (ROM) [p. 37] Typical values of R (b)Tl SN5488A, SN7488A and 5 are 256-bit ROM [p. 9-235] listed in Table ll ofspecification 8 memory 18 I Note interval posts. 8260 arithmetic TABLE A- Continited Conventional integrated Circuit (or other reference) Component (FIG, I)

Remarks Counter 2] (a)SlG 828] sixteen-state binary counter [p. 123], and a SIG 8250 binaryto-octal decoder Clock 20 Any oscillator I T|=Tcxas Instrument Co,

[Page references are to the TI Integrated Circuits Catalog for Design Engineers", First Edition, January, I972] SIG=Signctics Sunnyvale, California Flores, lvan "Computer Logic" Prentice-Hall. I960 Lcdley, Robert "Digital Computer and Control Engineering" McGraw-Hill, i960 intending to claim all novel, useful and unobvious features shown or described, the applicant makes the following claims: v

1. Apparatus for production of celeste in a computo organ comprising:

first means operative during repetitive computation intervals, for separately calculating a first set of Fourier components associated with the musical waveshape of a first note of one pitch; and second means, also operative during said repetitive computation intervals, for separately calculating a second set of Fourier components associated with the musical waveshape of a'second note having a pitch slightly offset in frequency with respect to said first -nte,

means for combining the calculated components of said first and said second sets within each computation interval to establish a sample point amplitude of a resultant musical waveshape the shape of which varies in time as a result of the frequency difference between said first and second notes.

means operative at the end of each computationinterval for incrementing the effective sample point for which said resultant waveshape amplitude is established. and

means for converting said resultant waveshape amplitudes to sounds in real time, the sounds so produced exhibiting a celeste effect.

2..Celeste-produ ction apparatus according to claim 1 wherein said calculatingand combining is performed digitally, wherein said means for converting includes adigital-to-analog converter and a sound system for reproducing the output from said converter, and wherein each component amplitude is established by a set of coefficients stored digitally, the relative amplitudes of said components establishing the tonal quality of the produced sounds. v

3. Celeste production apparatus according to claim 1 wherein components of said first set are calculated at effective waveshape sample points separated by qR wherein R is a frequency number establishing the fundamental period of said first note and q is an integer incremented at the end of each computation interval and wherein components of said second set are calculated at effective waveshape sample points separated by q(R 6) wherein 6 is a value designating the amount of frequency offset of said second note.

4; Celeste production apparatus according to claim 1 comprising:

a clock for establishing said repetitive computation intervals, a' frequency number'memory storing values R which establish the effective waveshape sample point separation for corresponding notes, a 8 memory storing harmonic offset values 8 for selectable notes, i a keyboard for selecting notes to be produced by said apparatus, actuation of a key on said keyboard causing memory readout of the R and 8 values for the selected note, note interval adders for establishing values of (qR) and q(R' 6) for selected notes during successive computation intervals, where q is an integer incremented by said means for incrementing, and wherein said'first means comprises circuitry, cooperating withsaid note interval adders,

for evaluating said-first set F) of Fourier components in accordance with the relationship and wherein said second means comprises circuitry,

also cooperating with'said note interval adders, for evaluating said second set F',,"" of Fourier components in accordance with the-relationship Fr c, a WM a 8) wherein A'and B represent the number of Fouriercomponents includes in said respective first and 1 second sets, components insaid second set being shifted in frequencywith respect to saidfirst set by an amount established by said values 8, wherein C, and C,,' are coefficients indicating the relative amplitude of the corresponding n' component in the respective first and second set, and wherein N is a system constant. 5 As a musical instrument exhibiting a: first means for computing at regular'time intervals t, the amplitudes x (qR) of a waveshape, where q is an'integer incremented each time interval 2,, in accordance with the relationship plitudes of the corresponding n'" components in the rea sinusoid table comprising a memory storing values of sin (2'r'r/N) for 0 0 $-N at intervals of D where D is a resolution constant,

afrequency number memory containing values of R associated with selectable musical notes, a '0 memory containing values of 8 associated with said notes, and note selection circuitry for'accessing from said frequency number and 8 memories the values R and 8 for each selected note,

harmoniccomponent evaluation circuitry utilizing said coefficient memory and said sinusoid table to calculate.

for each of the A Fourier components in said first set in accordance with the selected value R, and to calculate F sin (Z'rr/N) nq(R (n 1,2,. .B) for each of the B Fourier components in said second set -in accordance with the selected values R and 8, and

an accumulator for algebraically summing the calculated values 1 and F to obtain each waveshape amplitude X..(qR), and

second means responsive to said first means for providing celeste tones from said computed ampli tudes.

6. A musical instrument according to claim 5 wherein saidcalculations are performed digitally, wherein said second means includes a digital-to-analog converter and a sound system for converting said obtained wave- I shape amplitudes to musical sounds exhibiting a celeste effect, successive cycles of said obtained waveshape being of different shape.

7. A musical instrument according to claim 5 wherein said first means includes:

16 "a clock and counter defining calculation subintervals within said regular interval t components of said subintervals. 8. A musical instrument according to claim 5 together with means for preventing calculation of components in said second set when notes having certain values of R are selected. I

9. A musical instrument according to claim 5 wherein A B.

" firstand secondfsets being calculated during said 1.0. A musical instrument according to claim 9 wherein C, C,. for corresponding values of n.

II. A musical instrument according to claim 9 wherein C, C,.' for corresponding values of n. r

12. A. musical instrument according to claim 5 wherein B l, the frequency of the single component in said second set being slightly higher than the .funda mental (n l) component of said first set.

13. A musical instrument according to claim 5 wherein N represents the number of waveshape sample points for the tone of lowest fundamental frequency produced by said instrument, and wherein A+B M2.

14. A musical instrument according to claim 5 wherein the components of said first set are harmonically related in frequency to the true pitch of a selected note and wherein each component of said second set is offset slightly higher in frequency from the corresponding component of said first set. 7

15. A musical instrument according to claim 5 wherein the values 6 are selected so that the frequency offset of the (n 1)" component of said second set is in the range of from about 2 Hz to about 4 Hz.

16. A musical instrument according to claim 5 wherein said first means includes parallel processing said first and second sets.

* i ll 

1. Apparatus for production of celeste in a computor organ comprising: first means, operative during repetitive computation intervals, for separately calculating a first set of Fourier components associated with the musical waveshape of a first note of one pitch; and second means, also operative during said repetitive computation intervals, for separately calculating a second set of Fourier components associated with the musical waveshape of a second note having a pitch slightly offset in frequency with respect to said first note, means for combining the calculated components of said first and said second sets within each computation interval to establish a sample point amplitude of a resultant musical waveshape the shape of which varies in time as a result of the frequency difference between said first and second notes, means operative at the end of each computation interval for incrementing the effective sample point for which said resultant waveshape amplitude is established, and means for converting said resultant waveshape amplitudes to sounds in real time, the sounds so produced exhibiting a celeste effect.
 2. Celeste production apparatus according to claim 1 wherein said calculating and combining is performed digitally, wherein said means for converting includes a digital-to-analog converter and a sound system for reproducing the output from said converter, and wherein each component amplitude is established by a set of coefficients stored digitally, the relative amplitudes of said components establishing the tonal quality of the produced sounds.
 3. Celeste production apparatus according to claim 1 wherein components of said first set are calculated at effective waveshape sample points separated by qR wherein R is a frequency number establishing the fundamental period of said first note and q is an integer incremented at the end of each computation interval and wherein components of said second set are calculated at effective waveshape sample points separated by q(R + delta ) wherein delta is a value designating the amount of frequency offset of said second note.
 4. Celeste production apparatus according to claim 1 comprising: a clock for establishing said repetitive computation intervals, a frequency number memory storing values R which establish the effective waveshape sample point separation for corresponding notes, a delta memory storing harmonic offset values delta for selectable notes, a keyboard for selecting notes to be produced by said apparatus, actuation of a key on said keyboard causing memory readout of the R and delta values for the selected note, note interval adders for establishing values of (qR) and q(R + delta ) for selected notes during successive computation intervals, where q is an integer incremented by said means for incrementing, and wherein said first means comprises circuitry, cooperating with said note interval adders, for evaluating said first set FA(n) of Fourier components in accordance with the relationship FA(n) Cn sin (2 pi /N) nqR and wherein said second means comprises circuitry, also cooperating with said note interval adders, for evaluating said second set FB(n) of Fourier components in accordance with the relationship FB(n) Cn'' sin (2 pi /N) nq (R + delta ) wherein A and B represent the number of Fourier components includes in said respective first and second sets, components in said second set being shifted in frequency with respect to said first set by an amount established by said values delta , wherein Cn and Cn'' are coefficients indicating the relative amplitude of the corresponding nth component in the respective first and second set, and wherein N is a system constant.
 5. As a musical instrument exhibiting a: first means for computing at regular time intervals tx the amplitudes xo (qR) of a waveshape, where q is an integer incremented each time interval tx, in accordance with the relationship
 6. A musical instrument according to claim 5 wherein said calculations are performed digitally, wherein said second means includes a digital-to-analog converter and a sound system for converting said obtained waveshape amplitudes to musical sounds exhibiting a celeste effect, successive cycles of said obtained waveshape being of different shape.
 7. A musical instrument according to claim 5 wherein said first means includes: a clock and counter defining calculation subintervals within said regular interval tx, components of said first and second sets being calculated during said subintervals.
 8. A musical instrument according to claim 5 together with means for preventiNg calculation of components in said second set when notes having certain values of R are selected.
 9. A musical instrument according to claim 5 wherein A B.
 10. A musical instrument according to claim 9 wherein Cn Cn'' for corresponding values of n.
 11. A musical instrument according to claim 9 wherein Cn not = Cn'' for corresponding values of n.
 12. A musical instrument according to claim 5 wherein B 1, the frequency of the single component in said second set being slightly higher than the fundamental (n 1) component of said first set.
 13. A musical instrument according to claim 5 wherein N represents the number of waveshape sample points for the tone of lowest fundamental frequency produced by said instrument, and wherein A+B < or = N/2.
 14. A musical instrument according to claim 5 wherein the components of said first set are harmonically related in frequency to the true pitch of a selected note and wherein each component of said second set is offset slightly higher in frequency from the corresponding component of said first set.
 15. A musical instrument according to claim 5 wherein the values delta are selected so that the frequency offset of the (n 1)th component of said second set is in the range of from about 2 Hz to about 4 Hz.
 16. A musical instrument according to claim 5 wherein said first means includes parallel processing channels for concurrently calculating components of said first and second sets. 